# a subroutine returns a ref to a database handle...
my $pdb = &openDatabase();

# the ref to the db handle is passed to a subroutine as an
# optional hash element...
&doSomething(DB=>$pdb,FOO=>'bar');

# the subroutine assigns the ref to a scalar if it was
# passed, or directly obtains one of its own if it wasn't,
# does its thing, then closes the db handle if 
# it opened it...
sub doSomething
{
  my(%param)=@_;
  
  # we assign the ref to $rdb if it's defined, or open the
  # database for the first time if it's not
  my ($rdb) = ((defined($param{'DB'})) && ($param{'DB'})) ? $param{'DB'} : &openDatabase();
  
  # the subroutine does something useful...
  
  $$rdb->disconnect if(!(defined($param{'DB'})));
  return('done');
}